There are many industrial thermal fluid heat exchangers in use today. Many of them use a combustible oil as the circulating fluid. For example, in the wood panel manufacturing field many operating plants have a thermal oil heat exchanger in order to heat oil to temperatures whereby it can then be used to heat the hot presses within the plant. The heat exchangers are constructed within the exhaust ducting of typical industrial boilers. Unfortunately the gaseous stream from the combustion process can be quite hot (temperatures .+-.1,000.degree. F. are common) and act to ignite any oil that flows from a leak within the closed circuit of the heat exchanger. Of course, continuous maintenance on the heat exchanger tubes will serve to reduce the occurrence of leaks but when one occurs, it would be very advantageous to have an automatic fire suppression system which controls the unwanted combustion, thereby preventing damage.
For example, in many thermal oil heat exchangers the flash point for a typically used oil is 380.degree. F. The hot combustion exhaust gas stream can be at 1000.degree. F. when entering the inlet end of the heat exchanger and if there is an oil leak, flashover will occur because the exhaust gas has enough oxygen to support combustion. 0n typical boilers using heat exchangers of the present type there can be residual oxygen in the range of 20% within the gas stream whereas it is usually felt that an oxygen level of 15% is the minimum amount required to support combustion.
Given these typical operating parameters, where an oil leak could result in a damaging fire, it has become a virtual requirement that some form of fire control means be provided. The present invention represents an improved fire suppression means for the general type of hot gas/flammable liquid environment where the hot gas can support combustion within a conduit. Our invention provides a source of liquid, external to the conduit, which is sprayed into the conduit when a fire is detected and is directed towards locations strategic to the source of the flammable fluid within the conduit. Nozzles create a fine mist spray and when the high temperature environment (fire conditions) transfers heat to the cooler spray it becomes steam which can then provide a cooling and smothering function as it is exhausted from the conduit. A sufficient amount of the fire control liquid is pumped through the nozzles to, in turn, create sufficient steam to supplant enough of the oxygen within the hot gas stream so that the steam can act to "snuff out" the fire. After the fire is controlled, suppressed and terminated, measures can be taken to repair leaks.
Thus, from the foregoing, one object of the present invention is to suppress a fire within a hot gas conduit having a source of flammable material therein.
Another object is to rapidly create an atmosphere within a hot gas conduit having an oxygen content below that which supports combustion of the flammable material therein.
Yet a further object is to reduce the temperature within the hot gas conduit about the area providing the source of flammable material thereby cooling the internal temperatures to levels that are safe.
These and other objects will become apparent upon reviewing the detailed description to follow in conjunction with the attached drawings.